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VMWare, Performance (with only one VM on a machine)

Posted on 2012-03-15
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In a situation where there is one, and only one VM on a machine, are you relieved from having to worry about assigning too many vCPUs to a VM

If I only have a single VM, can I simply assign all more cores to the VM and go, since the scheduler does not have to swap processors until they are available ?

Same with memory, if I only have a single VM, can I assign it all the memory, or evern half the memory, without worrying about swapping ?
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Question by:Los Angeles1
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by:thomasdavis
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If your asking if you can assign all the memory and cpu's to one vm on a vm host the answer is yes.
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by:Alan_White
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Yes, but...

The hypervisor will need some processor and RAM too.  

So you can either accept that some scheduler swapping will occur or leave some processor and RAM asside for the hypervisor.
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by:Andrew Hancock (VMware vExpert / EE MVE)
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its a complete waste or resources and your VM will not benefit, as previous discussions we have had on the subject.
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by:Los Angeles1
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its a complete waste or resources and your VM will not benefit, as previous discussions we have had on the subject.

This is what I was getting at in the question.

In the previous discussion, it was correctly pointed out to me that the scheduler swapped CPU and Memory between the VM's, thus assigning lots of CPU and memory would probably slow it down

So what I was thinking was that if I only use a single VM on a host, the scheduler would not get involved swapping resources.

Why is my thinking wrong ?  Am I wrong about the scheduler not being active with only a single VM ?

Thanks
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Andrew Hancock (VMware vExpert / EE MVE) earned 500 total points
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Yes, your thinking if kind of correct, but why would you then use a Hypervisor with a single VM!

You might as well, install on the Bare Metal, and the OS, will have full use of ALL the resources, without the Hypervisor in between hardware and OS!
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by:Andrew Hancock (VMware vExpert / EE MVE)
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It's the CPU Scheduler! (nothing to do with memory!).
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